LEDs have become common in many lighting applications. For example, linear LED light engines are employed in luminaires for store display lighting. An issue with such linear LED luminaires is directing the emitted light in such a way to gain the best light distribution for the purpose of illuminating the items being displayed or the store in general.
LED luminaires typically emit light in a diffuse or lambertian light intensity distribution pattern such that the luminance is the same when viewed from any angle. The projection of a lambertian distribution onto a flat surface results in areas of high illuminance directly under the source and areas of lower illuminance away from the source. Thus, luminaires with lambertian distributions are suboptimal in many applications.
A batwing distribution provides increased uniformity when projected onto a plane due to the increased amount of light directed off the primary optical axis. It would be advantageous to have linear LED luminaires that achieve batwing distribution and are useful for lighting store displays.
Controlling the light output and providing batwing distribution is possible by using special refractive lenses for direct lighting systems. This will not work for non-white LEDs however because different colors will appear from the fixture. Another way to control the light distribution is using a metallic reflector, but this creates an image of the light source on the reflector and can cause glare and be objectionable to the customer. The above-described shortcomings significantly limit the usefulness of linear LED luminaires.